Silver Springs 100 year Capture Zone

100-year Capture Zones represent the distance and direction water particles in the aquifer travel in a 100-year period before reaching a spring head. The boundaries of the geographic area that contributes groundwater to the Silver Springs spring group are dynamic and can be influenced by changing climatic conditions and by anthropogenic conditions, such as groundwater withdrawals. Groundwater within the spring recharge basin (springshed) potentially emerges as discharge from the Silver Springs spring group. The USGS MODFLOW numerical code was the basis for a regional groundwater flow model encompassing north-central Florida. This model was used to simulate the groundwater flow conditions as influenced by groundwater withdrawals that occurred in 1999. The results of the 1999 simulation were then applied to the USGS MODPATH particle-tracking code. This code allows for the determination (mapping) of the origin of groundwater contributing to a specific area of interest within the model by using the reverse particle tracking method. This method traces the flowpaths of a prescribed number of water particles from their points of discharge backward to the original point of origin or to a location determined by the estimated time of travel. In this case, the model grid cell that encompasses the Silver Springs spring group is the particle point of discharge. Further documentation of this methodology is provided in the following SJRWMD special publication: , search https://www.sjrwmd.com for SP/SJ2007-SP4.pdf The delineated 100-year capture zone represent the estimated geographic extent of areas within which it would take groundwater 100 years to travel to the discharge point at the Silver Springs spring group. The capture zone delineations are influenced by the hydrogeologic characteristics of the Surficial aquifer system (SAS) and the Floridan aquifer system (FAS) present within these areas. Horizontal groundwater flow in the Upper Floridan aquifer is, in general, the dominating factor that determines the extent of the capture zone boundaries. Note: The 1000-year capture zone encompasses nearly all of the Silver Springs recharge basin. The 1000-year capture zone in combination with an interpretation of groundwater flow direction within the upper Floridan aquifer is used to delineate the springshed boundary for the Silver Springs spring group.百年捕获区指含水层中的水团在抵达泉头前，于100年时间内运移的距离与方向。为银泉群补给地下水的地理区域边界属于动态边界，可受气候变化以及地下水开采等人为活动影响。 该泉补给流域（springshed，泉域）内的地下水，最终可能以银泉群排泄的形式出露地表。本次研究以美国地质调查局（USGS）的MODFLOW数值代码为基础，构建了涵盖佛罗里达中北部的区域地下水流模型。该模型被用于模拟1999年地下水开采条件下的地下水流状态。 随后将1999年的模拟结果应用于美国地质调查局（USGS）的MODPATH粒子追踪代码。该代码可通过反向粒子追踪法，完成模型内特定关注区域的地下水补给来源的确定与制图。该方法通过从预设数量的水团排泄点出发，反向追溯其运移路径至初始补给点，或追溯至由估算运移时间确定的位置。本次研究中，包含银泉群的模型网格单元格即作为水团的排泄点。 该方法的详细文档可参阅以下南佛罗里达水管理区（SJRWMD）专项出版物：可在https://www.sjrwmd.com 搜索SP/SJ2007-SP4.pdf获取。 本次勾绘的百年捕获区，代表了地下水需耗时100年才能运移至银泉群排泄点的估算地理范围。捕获区的勾绘结果受上述区域内表层含水层系统（Surficial aquifer system, SAS）与佛罗里达含水层系统（Floridan aquifer system, FAS）的水文地质特征影响。总体而言，上佛罗里达含水层的水平地下径流是决定捕获区边界范围的主导因素。 注：千年捕获区几乎覆盖了银泉补给流域的全部范围。结合千年捕获区与上佛罗里达含水层内地下水流方向的解译结果，可勾绘出银泉群的泉域边界。